INTERPRETATION OF LOCAL GRAVITY ANOMALIES IN NORTHERN NEW YORK

About 10,000 gravity measurements were made in the Adirondack Mountains Lake Champlain Valley, St Lawrence River Valley, and Tug Hill Plateau. The closely spaced gravity measurements were compiled to construct computer contoured gravity maps. These maps reveal local anomalies related to seismicity, faults, mineral deposits and gas fields that are not seen on regional gravity maps.

In northern New York gravity maps indicate epicenters of earthquakes are concentrated in areas of most pronounced gravity anomalies along steep gravity gradients. In the epicentral region of the Au Sable Forks earthquake gravity mapping reveals a north–south trending fault separating a gravity low on the west from high gravity in the east. In the St. Lawrence Valley, the Carthage-Colton Mylonite Zone is along steep gravity gradients extending into eastern Lake Ontario. In Russell, NY, a small circular gravity high coincides with a cluster of earthquake epicenters.

Gravity and magnetic surveying at the closed Benson Magnetite mine revealed anomalies indicating significant amounts of magnetite possibly occurring at shallow depths and a detailed gravity map at the Sylvia Lake Zinc district indicates a gravity high over the ore deposits.

In the Lake Champlain Valley, a northeast trending gravity high is related to a fault and a circular shaped gravity high not of Plattsburg is related to a buried high density pluton. Near Morristown, NY, gravity and magnetic anomalies occur over the Morristown fault and gravity mapping in the Tug Hill Plateau indicates gravity anomalies related to abandoned gas fields at Camden, Sandy Creek, and Pulaski.